Rotary instruments for indicating linear measurements

ABSTRACT

A compact rotary dial unit for accurately measuring small movements of a machine-tool lead-screw, the unit having one continuous decimally divided scale which indicates the measurement in either the metric or the inch system, as initially selected by the operator; the unit encloses an epicyclic gearing which when changed from a nonoperating to an operating condition causes a change (simply related to 2.54) in the rotation speed of the scale.

, States Patent Medurst 1451 my 2 H72 [54] RUTARY HNSTRUMENTS FORHNIDHCATING LINEAR MEASUREMENTS Cyril W. Medhurst, Woking, EnglandBritish Aircraft Corporation, London, England Oct. 8, 1969 Inventor:

[73] Assignee:

Filed:

App]. No.:

[30] Foreign Application Priority Data Oct. 25, 1968 Great Britain..50,852/68 US. Cl."

Int. Cl

Field of Search ..ll6/l 15.5, 33/126 ..B23q 17/00 ...1 16/1 15, 115.5,124; 33/126; 74 10, 813

. 2 [95/ I? 52 b If Primary Examiner-Louis J. Capozi AttorneySughrue,Rothwell, Mion, Zinn & Macpeak [5 7] ABSTRACT A compact rotary dial unitfor accurately measuring small movements of a machine-tool lead-screw,the unit having one continuous decimally divided scale which indicatesthe measurement in either the metric or the inch system, as initiallyselected by the operator; the unit encloses an epicyclic gearing whichwhen changed from a nonoperating to an operating condition causes achange (simply related to 2.54) in the rotation speed of the scale.

12 Claims, 8 Drawing Figures PAIENTEDMAR28 1972 SHEET 3 OF 4 W; 4 R\ I 47 mwm/ H Fran/A m ROTARY INSTRUMENTS FOR INDICATING LINEAR MEASUREMENTSThis invention relates to rotary instruments for indicating linearmeasurements in English and Metric units alternatively. It isparticularly concerned with such instruments for indicat ing the extentof linear movements imparted by rotary movement of a lead screw, e.g.,in a machine tool. Rotary instruments with cylindrical scales, otherwiseknown as dial units, which measure linear displacement in terms ofrotation of a lead screw, are employed on a number of difierent types ofmachine tools. Generally speaking, such dial units have a scale readingin English units or a scale reading in Metric units. With the increasinguse of the Metric system in English speaking countries, the requirementto change a tool over from operation in the one system to operation inthe other, and back again, is occurring more frequently. It is notpracticable simply to provide two separate scales, one in English andone in Metric units, rotating at the same speed, because one revolutionof each scale must correspond with a decimal number (1, 10, 100 etc.) ofunits of length if the scale is to be easily readable after completionof more than one revolution, and the ratio between the English andmetric units (inchzcentimeter) is 1:2.54. Provision of two scales sideby side and geared together can be difficult because of the lack ofspace in many machine tools. The presence of two simultaneously visiblescales might also confuse the operator.

It is an object of the present invention to provide a rotary instrumentor dial unit of compact construction, having a scale capable of easy andrapid conversion from reading in English units to metric units, and viceversa.

According to the present invention, a rotary instrument for indicatinglinear measurement in English and metric units alternatively, comprisesan epicyclic gearing which has three main components, namely aplanet-carrier carrying planet wheels, a sun gear, and an internallytoothed ring gear, both of the latter components meshing with the planetwheels, one of the three components being adapted to be secured on ashaft, the rotational movement of which is proportional to a linearmovement to be measured, a second one of the three components carrying ascale which is read against a relatively fixed mark, and there beingmeans for clamping the third of the components alternatively to one ofthe other components or to the stationary member, so that the componentcarrying the scale will rotate either at the same speed as the shaft, orat a fixed velocity ratio thereto, the gearing being such that the saidratio corresponds to or bears a simple relation to, the ratio betweenEnglish and metric units of length.

By means of the invention, a complete revolution of the scale-carryingmember can correspond to either of two selectable axial linearmovements, the one movement being a simple inch-based unit, and theother a simple metric unit.

The clamping means may comprise frictionally engageable surfaces whichact as clutches, the changeover from clamping the third component toanother component of the gearing, to clamping it to the stationarymember, being effected by shifting the third component axially.

Preferably this axial shifting movement is effected manually bypartially rotating an external ring member which is arranged to moveaxially on such partial rotation, the ring member carrying two marksagainst either of which the scale can be read together with indicationsof which unit is appropriate to each mark, only one such mark andindication being visible to the operator at one time- The compactconstruction made possible by the invention enables the instrument inmany cases to be fitted in place of an existing dial unit reading inonly one system of length units.

Various embodiments of the invention will now be described in moredetail by way of example and with reference to the accompanyingdrawings, in which:

FIG. 1 is a part-section part-plan view of a rotary instrument or dialunit according to the invention, adjusted to measure in inches;

FIG. la is a scrap view of the dial unit adjusted to measure inmillimeters;

FIG. 2 and 2a are similar views of another embodiment of the invention;

FIGS. 3 and 3a are similar views of a further modification; and

FIGS. 4 and 4a are similar views of yet another modification.

The embodiments shown in the accompanying drawings are intended for useon machine tools, adjacent to a hand-wheel indicated at W, forindicating the linear displacement imparted to an element of the machinetool by rotation of the hand-wheel W and of a lead screw (not shown) towhich it is connected by the shaft S.

In the embodiment shown in FIGS. 1 and 1a, a planet-carrier 1 is mountedon the shaft S for rotation therewith. Planet wheels 7 carried by theplanet carrier 1 mesh with an internally toothed ring gear 5 and with asun gear 61 formed on a member 6 which also carries a cylindricalgraduated scale 8. The scale 8 is held from rotation with respect to themember 6 by means of friction devices (preferably two in number) eachcomprising a ball 14 pressed outwards into an annular recess in theunderside of the scale 8 by means of a rubber pressure pad 15accommodated in a pocket in the member 6. An annular backing member 3 isheld stationary by bolts (not shown) screwed into a stationary part ofthe machine tool. A knurled unit-selector ring 2 is rotatable on thebacking member 3 through approximately half a turn, such partialrotation being accompanied by a slight axial movement due to a screwthread engagement between the unit-selector ring 2 and the backingmember 3.

The ring gear 5 is arranged for axial movement with the selector ring 2.A thrust bearing comprising balls 11 is interposed between the selectorring 2 and the left-hand side of an outwardly extending flange 51 on thering gear 5 while a lock ring 12 projecting inwardly from the right-handend of the selector ring 2 is arranged to bear against the right-handside of the flange 51, a small amount of play being allowed to ensurethat when the flange 51 is engaged by the balls 11 it is free from thelock ring 12.

The ring gear 5 has a conical face 19 capable of engaging acorresponding conical face 20 on the backing member 3. It also carries aresilient O-ring 13 capable of engaging a surface 62 on the sun gearcarrying member 6. These two combinations serve as clutches respectivelyfor Metric and English measurements.

The sun gear carrying member 6 is retained on the planetcarrier 1 by acirclip 9, while the planet-carrier 1 is restrained from axial movementby a thrust washer 4 which is retained by a circlip l0 and engages aball bearing 18 in the stationary backing member 3. In FIG. 1 theresilient O-ring 13 is shown compressed between a surface 52 on theinternal ring gear 5 and the surface 62 on the sun gear carrying member6. The O- ring 13 engages the surfaces 52 and 62 in this way only solong as the selector ring 2 is in the rightward position shown, and isexerting pressure on the ring gear 5 via the balls 11.

In this position, the components 5, 6 and 7 of the epicyclic gearing arelocked together so that the member 6 which carries the scale 8 rotatesat the same speed as the planet-carrier 1 and the shaft S. The selectorring 2 presents to the operator a mark 16 and an indication (only partlyshown) that the scale is reading in thousandths of an inch.

If the selector ring 2 is now rotated through thereby shifting theselector ring 2 and the ring gear 5 to the left and releasing theengagement of the O-ring 13 between surfaces 52 and 62, the conicalsurface 19 on the internal ring gear 5 will engage the conical surface20 on the back-plate 3. The internal ring gear 5 will then be locked tothe stationary part of the machine tool by reason of the pressureexerted via the lock ring 12. Rotation of the shaft S and planet-carrier1 now causes rotation of the sun gear 61 and hence of the scale 8 atincreased speed. The numbers of teeth on the ring gear 5 and the sungear 61 are chosen in the ratio 154/100 so as to give a velocity ratioof 2.54 to 1. At the same time the selector ring 2 now presents to theoperator a second mark 17 (FIG. 1a) and an indication that the samescale now reads in hundredths of a millimeter.

Zero setting may be achieved by rotating the scale 8 by means of itsknurled ring K, the friction devices formed by the balls 14 and rubberpressure pads 15 being arranged to slip at a convenient torque figure.

It may not always be convenient to have the scale rotating at 2.54 timesnormal speed when operating on the metric system. The instrument shownin FIGS. 2 and 2a has been designed to overcome this difficulty.

In this embodiment of the invention, the planet-carrier 21 is againmounted on the shaft S, but it carries pairs of coupled planet-wheels29, 30, of different diameters. The larger diameter planet-wheels 29mesh with the sun gear 25 which is formed on an axially shiftable member31. The smaller diameter planet-wheels 30 mesh with an internal ringgear 44 on a scale-carrying member 32. Conical surfaces 33, 34 on themember 31 are arranged to cooperate alternatively with similar surfaceson the planet-carrier 21 and on an inwardly extending flange 26 on theselector ring 35, respectively. The selector ring 35 is rotatablethrough 180 on the backing member 36, and is screw-threaded thereon soas to cause such rotation to be accompanied by a small axial movement.The backing member 36 is held stationary by a dowel peg 38 fitting intoa corresponding recess in a stationary part of the machine tool. Theassembly is retained as before by circlips 39, 40 on the planet-carrier21, engaging the outer faces of thrust bearings 41, 42.

The scale 43 is visible through one of two windows 27, 28 in theselector ring 35, according to the position of the latter. On theright-hand side of the graduations are shown figures for use in inchmeasurements, and on the left figures for metric measurements. Thewindows 27, 28 are offset, as can be seen by comparison of FIGS. 2 and20, so that the appropriate set of figures only can be seen. The windows27, 28 carry respective marks 23, 24 for reading the scale 43.

A resilient O-ring 22 under compression between the axially shiftablemember 31 and thrust bearing 41 urges the member 31 to the left into theposition shown in FIG. 2, in which the member 31 carrying the sun gear25 engages the planet-carrier 21 through the conical surface 33 so thatthe gearing is locked and the member 32 carrying the internal ring gear44 and the scale 43 rotates with the shaft S.

Rotation of the selector ring 35 through 180 shifts the ring 35 to theright and thereby clamps the members 31 stationary through conicalsurface 34 and releases it from planet-carrier 21. The coupledplanet-wheels are so dimensioned that the member 32 carrying the scale15 is then rotated at a velocity ratio of 1.27:1 i.e., (2.54/2) 1. Thusthe scale reads either in 0.00 1-inch divisions or 0.02-millimeterdivisions.

Zero setting can be achieved by rotation of member 31, slipping the coneclutches 33, 34.

An alternative instrument, not shown, incorporates the principle ofhaving coupled concentric planet gears of different diameters, buthaving the scale carried by the sun gear, the axially movable componentbeing the ring gear, in the manner seen in FIG. 1. The scale can becaused to rotate at any reasonable rate faster than or slower than itwould were there only one planet gear, by suitably selecting therelative diameters of the two planet gears.

FIGS. 3 and 3a show a modification of the embodiment of FIGS. 2 and 2a.The planet-carrier 211, planets 291, 301, axially shiftable member 311carrying sun gear 251, scale-carrying member 321 carrying thefine-scale'431, and selector ring 351 are all similar to those describedwith reference to FIGS. 2 and 2a and operate in the same manner, Inaddition, a second scale 49 indicating the aggregate or coarse settingis included. For this purpose a second epicyclic gearing isincorporated, having a planet-carrier 50 secured to the fine scalecarrying member 321, coupled pairs of planet-wheels 51,52 and aninternal ring gear 53 on the stationary backing-member 56 meshing withplanets 51. Planets 52 are caused to rotate slowly with planets 51 asthe planet-carrier 50 rotates, and

mesh with a second internal ring gear 54 on an annular member 55carrying the second scale 49. Planets 52 have a slightly lesser numberof teeth than planets 51 and so drive the member 55 with a highreduction. The gearing may be arranged so that the velocity ratiobetween the scale-carrying members 321 and 55 is l, for example. Pairsof windows 271,272 and 281,282 are provided in the selector ring 351 forviewing the inch and metric scales respectively.

FIGS. 4 and 4a show a modification of the embodiment of FIGS. 3 and 3a,in which the velocity ratio between the fine and coarse scales isfurther increased by omitting the second planet-carrier 50 of FIG. 3 andreplacing it by a rotatable annular member 60 which connects the finescale carrying member 322 to a further sun wheel 61 meshing with planets511, which also mesh with the stationary ring gear 531 as before. Theplanets 511, 521 are mounted on a free annular carrier 62 which rotatesslowly as member 322 rotates. Planets 521 mesh with internal ring gear541 on the member 551 carrying the second scale 491 and drive it with ahigh reduction. With this arrangement, the velocity ratio between themembers 322 and 551 may be as high as 250:1 or even 400:1.

The features seen in FIGS. 3 and 4, namely of having second epicyclicgearings to provide coarse readings can be incorporated into thearrangement seen in FIGS. 1 and 1a, by arranging the sun gear (thescale-carrying member) either to mesh with one of a pair of planet gearsof slightly different diameters as seen in FIGS. 4 and 4a, or to carry afurther planet carrier having two planet gears, as seen in FIGS. 3 and3a.

Iclaim:

l. A rotary instrument for indicating linear movements of a movablemember in English and metric measurement units alternatively, theinstrument comprising a rotatable shaft which is operatively connectedto the movable member such that the rotational movement thereof isproportional to the linear movement of the movable member; an epicyclicgearing which has a planet-carrier carrying planet gear wheels, a sungear, an internally toothed ring gear; said sun gear and said ring gearbeing in meshing engagement with said planet wheels, said planet carrierbeing secured to said shaft, one of said sun gear and said ring gearcarrying a scale; a stationary member; and means for clamping the otherof said sun gear and said ring gear alternatively to said planet-carrieror said one of said gears so that the latter will rotate at the samespeed as said shaft, or to said stationary member so that said one ofsaid gears will rotate at a fixed velocity ratio relative to said shaft,the gear ratios of said gear wheels, said sun gear and said ring gearbeing such that the said velocity ratio corresponds to or bears a simplerelation to the ratio between English and metric units of length, saidclamping means comprising a mark against which said scale can be read.

2. An instrument according to claim 1, in which the clamping meanscomprise frictionally engageable surfaces which act as clutches betweensaid planet carrier, said sun gear, said ring gear and/or saidstationary member, the changeover from clamping the other of said gearsto said planet-carrier or the one of said gears, to clamping it to thestationary member, being effected by shifting the other of said gearsaxially.

3. An instrument according to claim 2, wherein said clamping meanscomprises an external selector ring member mounted for rotational andaxial movement on said stationary member, and the axial shiftingmovement of the other of said gears is performed manually by partiallyrotating said external selector ring member, the ring member carryingtwo marks against either of which the scale can be read, there beingrespective indications of which unit is appropriate to each mark, onlyone such mark and indication being visible to the operator at one time.

4. An instrument according to claim 1 in which the scale is carried bythe sun gear, and the ring gear is the other of said gears.

5. An instrument according to claim 1 in which the ring gear carries thescale, and the sun gear is the axially movable component.

6. An instrument according to claim 1 in which there are two concentricplanet gears of different diameters which are rigidly coupled forrotation, one planet gear meshing with the axially shiftable member, andthe other with the gear member which carries the scale.

7. An instrument according to claim 6 in which the sun gear is axiallymovable and meshes with the larger planet gear, and ring gear carriesthe scale and meshes with the smaller planet gear.

8. An instrument according to claim 7 in which the scale carries twoseries of graduations which are axially spaced from one another, and theselector ring member is a partially rotatable sleeve, the rotation ofwhich axially moves the movable member, the sleeve having twocircumferentially spaced windows, each of which exposes the scaleappropriate to the angular setting of the sleeve and the consequentaxial position of the said movable member.

9. An instrument according to claim 1 in which there is a furtherplanet-carrier secured to the scale carrying ring, the furtherplanet-carrier carrying two further rigidly coupled Ill? concentricplanet gears of slightly different diameters, the larger of which mesheswith a stationary ring gear, and the smaller of which meshes with amovable ring gear which carries a further scale.

10. An instrument according to claim 1 in which the scalecarrying ringis coupled to a further sun gear with which meshes with slightly largerof a further pair of rigidly coupled planet gears, the larger planetgear also meshing with a stationary outer ring gear, and the smallerplanet gear meshing with a further scale-carrying ring.

11. An instrument according to claim 1 in which the scalecarrying one ofsaid gears comprises two parts, one of which carries the scale and hasfrictional engagement with the other part, which carries the gear teeththereof, the frictional engagement permitting zero setting of the scale.

12. An instrument according to claim 1 and comprising a unit selectorwhich is mounted to be frictionally and partially rotated about thestationary member and which carries two spaced marks against which thescale can be read.

1. A rotary instrument for indicating linear movements of a movablemember in English and metric measurement units alternatively, theinstrument comprising a rotatable shaft which is operatively connectedto the movable member such that the rotational movement thereof isproportional to the linear movement of the movable member; an epicyclicgearing which has a planet-carrier carrying planet gear wheels, a sungear, an internally toothed ring gear; said sun gear and said ring gearbeing in meshing eNgagement with said planet wheels, said planet carrierbeing secured to said shaft, one of said sun gear and said ring gearcarrying a scale; a stationary member; and means for clamping the otherof said sun gear and said ring gear alternatively to said planet-carrieror said one of said gears so that the latter will rotate at the samespeed as said shaft, or to said stationary member so that said one ofsaid gears will rotate at a fixed velocity ratio relative to said shaft,the gear ratios of said gear wheels, said sun gear and said ring gearbeing such that the said velocity ratio corresponds to or bears a simplerelation to the ratio between English and metric units of length, saidclamping means comprising a mark against which said scale can be read.2. An instrument according to claim 1, in which the clamping meanscomprise frictionally engageable surfaces which act as clutches betweensaid planet carrier, said sun gear, said ring gear and/or saidstationary member, the changeover from clamping the other of said gearsto said planet-carrier or the one of said gears, to clamping it to thestationary member, being effected by shifting the other of said gearsaxially.
 3. An instrument according to claim 2, wherein said clampingmeans comprises an external selector ring member mounted for rotationaland axial movement on said stationary member, and the axial shiftingmovement of the other of said gears is performed manually by partiallyrotating said external selector ring member, the ring member carryingtwo marks against either of which the scale can be read, there beingrespective indications of which unit is appropriate to each mark, onlyone such mark and indication being visible to the operator at one time.4. An instrument according to claim 1 in which the scale is carried bythe sun gear, and the ring gear is the other of said gears.
 5. Aninstrument according to claim 1 in which the ring gear carries thescale, and the sun gear is the axially movable component.
 6. Aninstrument according to claim 1 in which there are two concentric planetgears of different diameters which are rigidly coupled for rotation, oneplanet gear meshing with the axially shiftable member, and the otherwith the gear member which carries the scale.
 7. An instrument accordingto claim 6 in which the sun gear is axially movable and meshes with thelarger planet gear, and ring gear carries the scale and meshes with thesmaller planet gear.
 8. An instrument according to claim 7 in which thescale carries two series of graduations which are axially spaced fromone another, and the selector ring member is a partially rotatablesleeve, the rotation of which axially moves the movable member, thesleeve having two circumferentially spaced windows, each of whichexposes the scale appropriate to the angular setting of the sleeve andthe consequent axial position of the said movable member.
 9. Aninstrument according to claim 1 in which there is a furtherplanet-carrier secured to the scale carrying ring, the furtherplanet-carrier carrying two further rigidly coupled concentric planetgears of slightly different diameters, the larger of which meshes with astationary ring gear, and the smaller of which meshes with a movablering gear which carries a further scale.
 10. An instrument according toclaim 1 in which the scale-carrying ring is coupled to a further sungear with which meshes with slightly larger of a further pair of rigidlycoupled planet gears, the larger planet gear also meshing with astationary outer ring gear, and the smaller planet gear meshing with afurther scale-carrying ring.
 11. An instrument according to claim 1 inwhich the scale-carrying one of said gears comprises two parts, one ofwhich carries the scale and has frictional engagement with the otherpart, which carries the gear teeth thereof, the frictional engagementpermitting zero setting of the scale.
 12. An instrument according toclaim 1 and comprising a unit selector which is mounted To befrictionally and partially rotated about the stationary member and whichcarries two spaced marks against which the scale can be read.